The present invention is directed to a process for the production of a case or cover for a hard bound book utilizing a specific class of hot melt pressure sensitive adhesives.
Casemaking is a series of carefully synchronized procedures for making the cover of a hard bound book. In general, the material that will form the outer covering of the book, in precut or continuous web form is coated with adhesive, passed along a a conveyer under boards which have been precut to the exact size of the finished book cover, the boards are dropped in place and a center strip is laid down between the boards. If the cloth was not precut, it is then cut and, in either case, a portion of the cloth extends about 5/8 inch around the perimeter of the cover boards. This extension is then folded over the boards in a two step "turning-in" process with the sides folded first and the end folded to lap over the sides.
The adhesive used in order to construct the book cover or book case must possess certain critical properties. Because the operation is a multi-step one, the adhesive chosen must have a relatively long period of agressive tack so as to retain sufficient tack to instantly hold down the folded extensions without allowing them to spring back during the turning-in step. In addition to its agressive tack, the adhesive selected must have good machining properties, and it should be able to adhere a wide variety of case stock materials. Furthermore, once the case is formed, the adhesive must not penetrate the stock which would ruin the cover nor may it be affected by moisture, which could cause warping of the cover.
Heretofore animal glues have been the principal adhesives used for casemaking. These adhesives are, however, sensitive to moisture and are restricted in their use to a limited range of cover stocks. While some attempts have been made to use ethylene vinyl acetate hot melt adhesives that have been specially formulated to extend their open time, these adhesives have not met with success on a commercial scale.
It is therefore an object of the present invention to provide an adhesive suitable for use in case making operations, the adhesive being characterized by a long period of agressive tack, good machining properties and heat and moisture resistance.
It is a further object of the invention to provide such an adhesive which may be used on a wide variety of difficult to bond cover stocks.
These and other objects will be apparent from the description that follows.